Three attribute instances of the array object

Length PropertyDefinition and usage

The length property can set or return the number of elements in the array. This is very common.

Grammar

Arrayobject.length

Prototype PropertyDefinition and Usage

The prototype property gives you the ability to add properties and methods to an object.

Grammar

Object.prototype.name=value

Example

In this example, we will show how to use the prototype property to add properties to an object:

　　

1<script type= "Text/javascript" >2     //constructor Function3   functionEmployee (Name,job,born)4   {5    This. name=name;6    This. job=job;7    This. born=born;8   }9   //new instance, Bill, he inherits all the attributes of employeeTen  varBill=NewEmployee ("Bill Gates", "Engineer", 1985); One  //Add the Salary property to the employee prototype Aemployee.prototype.salary=NULL; -   //This property can be inherited by Bill to -bill.salary=20000; the   - document.write (bill.salary); -   -</script>

Output:

20000

Constructor property
The constructor property returns a reference to the array function that created this object.

<script type= "Text/javascript" > // constructor Function function Employee (Name,job,born) {this. name=name; this. job=job; this. born=born;} var bill=New employee ("Bill Gates", "Engineer", 1985);d Ocument.write (bill.constructor); </script>

Output:

1 function Employee (name, JobTitle, born) 2 {this this. Born = born;}

The result is that the constructor that created it is returned

Three attribute instances of the array object